Calcium action in synaptic transmitter release.

TLDR: Although the general role of Ca as a presynaptic messenger is well supported, many important specifics of its action remain to be resolved.

Abstract: In this review we are concerned with the mechanisms by which the electrical potential across the membrane of presynaptic nerve terminals regulates the release of neurotransmitter substances into the synaptic cleft . Ca ions play a central role in this process: Release occurs when a voltage-depen­ dent Ca channel in the presynaptic membrane opens, thus permitting an influx of Ca ions and diffusion of Ca in cytoplasm, followed by binding of Ca at some cytoplasmic site that triggers the exocytotic release of quanta of neurotransmitter. These concepts, introduced mainly by the work of Katz and associates (Katz 1 969), comprise the "Ca hypothesis" of trans­ mitter release, a hypothesis now widely accepted. Although the general role of Ca as a presynaptic messenger is well supported, many important specifics of its action remain to be resolved. We review progress with these details in three parts, corresponding to